if Tong were to say he didn't remember, then they won't be able to get to the bottom of the matter.

The apodosis is based on the protasis, why WON'T but not WOULDN'T?(I understand all rules regarding conditionals, but this sentence baffles me)

Could you help me?

A suggestion: ESL leaners ususally have questions, even one, relating to many aspects in English; it is not reasonable to devide a forum into so many parts that they have to confusedly to choose from when they want to post a question; apart from this, discussions should be allowed, why lock the post?